1. Field of the Invention
The present invention relates to a servo control of a data storage medium drive, and more particularly, to a data storage medium in which accurate tracking control is possible for a high density product by improving the servo pattern recorded on the disk, and a method of controlling tracking of a head on the disk.
2. Description of the Related Art
To improve the recording capacity of a hard disk, it is necessary to improve not only the data recording and reproduction capability but also the capability of controlling the position of a recording/reproducing head. In a conventional hard disk drive, a method of recording and reading position information on and from a disk for a servo control depends on a DC component of a signal detected by a fall-wave rectifier and an integrator using the presence of a burst signal.
The servo of a hard disk drive is classified according to the method of recording servo information on a disk where data is recorded. An embedded servo method is usually used to provide servo position information. In the embedded servo method, servo information is recorded on all surfaces of a disk at a predetermined interval and data is recorded on all other areas. A servo information section and a data information section are alternatively located in a single track on the disk. The servo information section, where information on the position of a head is recorded, includes track position information, a track address, index information, and search information. Actual data information is recorded in the data information section.
A method of controlling the position of a head according to the conventional technology is explained with reference to FIGS. 1A through 1D. Here, FIG. 1A shows a servo pattern recorded on a hard disk; FIG. 1B shows an output signal detected by the head; FIG. 1C shows sampling signals A, B, C and D; and FIG. 1D shows burst signals A, B, C and D.
The servo section of a disk is divided into several sections such as A, B, C and D. Signals that are recorded in each servo burst area of the sections A, B, C and D, the servo burst area corresponding to half the track width, are read and pass through full-wave rectification and integration to detect a DC component. By putting a boundary between a section where the value of the DC component detected from the A and B bursts becomes maximum and a section where the value of the DC component becomes minimum at the center of the track, and comparing the sizes of the DC components generated due to superposition of the two components, a degree of deviation of the head from the center of the track can be determined.
The above method can be effective when the recording density is low. However, as the recording density increases and the length of a bit of a servo signal is considerably reduced, the DC component of an output signal of the head can be affected in a section with no servo burst signal.
FIGS. 2A through 2D are views for explaining a problem when the length of a bit of a servo signal is considerably reduced as above. Here, FIG. 2A shows a servo pattern recorded on a hard disk; FIG. 2B shows an output signal detected by the head; FIG. 2C shows sampling signals A, B, C and D; and FIG. 2D shows burst signals A, B, C and D.
Referring to FIG. 2B, a transitional section from the S pole to the N pole in a section without a signal on a disk changes gradually, which is different from FIG. 1B, so that the output signals and burst signals of the xe2x88x921/2 and +1/2 sections of a head appear to be distorted. Thus, as shown in FIG. 2D, since the burst signals A, B, C and D are detected to be distorted, the position information cannot be identified accurately.
To solve the above problem, it is an objective of the present invention to provide a data storage medium having a servo signal by which a head output signal and a burst signal can be detected without distortion even when the length of a bit recorded on a disk is considerably reduced.
It is another objective of the present invention to provide a method of controlling tracking of a head by reading the recorded servo signal from a data storage medium drive.
Accordingly, to achieve the first objective, there is provided a data storage medium including a servo information area where information on the position of a head is recorded and a data information area where actual data information is recorded, in which the servo information area is divided into an A/B burst section and a C/D burst section, the A/B burst section having a servo pattern in which phases of burst signals A and B are recorded to be different from each other and the C/D burst section having a servo pattern in which phases of burst signals C and D are recorded to be different from each other.
It is preferred in the present invention that the servo pattern recorded in the A/B burst section includes the burst signal A recorded in the +1/2 head portion of the (nxe2x88x921)th track and the xe2x88x921/2 head portion of the nth track, and the burst signal B, having a phase different from the burst signal A, recorded in the +1/2 head portion of the nth track and the xe2x88x921/2 head portion of the (n+1)th track, corresponding to the portion where the burst signal A is recorded.
Also, it is preferred in the present invention that the servo pattern recorded in the C/D burst section includes the burst signal C recorded in the xe2x88x921/2 head portion 0f the (n+1)th track and the +1/2 head portion of the (n+1)th track, and the burst signal D, having a phase different from the burst signal C, recorded in the xe2x88x921/2 head portion of the n track and the +1/2 head portion of the nth track, corresponding to the portion where the burst signal C is recorded.
To achieve the second objective, there is provided a method of controlling tracking of a head to determine a degree of deviation of the head from the center of a track in a data storage medium drive, in which a servo information area, where information on a position of the head is recorded, is divided into an A/B burst section and a C/D burst section, and includes a servo pattern that phases of burst signals A and B are recorded to be different from each other in the A/B burst section and phases of burst signals C and D are recorded to be different from each other in the C/D burst section, the method comprising the steps of: detecting a burst signal recorded in the servo pattern as the head moves along a track; generating sampling signals A and B to have a phase difference as great as that between the burst signals A and B and generating sampling signals C and D to have a phase difference as great as that between burst signals C and D; generating the burst signals A, B, C and D from head output signals detected according to the sampling signals; and determining the degree of deviation of the head from the center of the track from the magnitudes of DC components of the burst signals.